CN108715986B - Method for improving room temperature plasticity of austenitic nickel titanium-based shape memory alloy by adjusting texture - Google Patents
Method for improving room temperature plasticity of austenitic nickel titanium-based shape memory alloy by adjusting texture Download PDFInfo
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- CN108715986B CN108715986B CN201810669737.0A CN201810669737A CN108715986B CN 108715986 B CN108715986 B CN 108715986B CN 201810669737 A CN201810669737 A CN 201810669737A CN 108715986 B CN108715986 B CN 108715986B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
- C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/006—Resulting in heat recoverable alloys with a memory effect
Abstract
The invention relates to a method for improving room temperature plasticity of an austenitic nickel titanium-based shape memory alloy, belonging to the technical field of metal material processing and manufacturing. Cutting a rolled original bar of the austenitic nickel titanium-based shape memory alloy into a cylinder with a certain height, embedding the cylinder into a low-carbon steel annular sheath with the same height, placing the austenitic nickel titanium-based shape memory alloy passing through the low-carbon steel sheath between an upper anvil plate and a lower anvil plate of a press, performing large plastic deformation at room temperature, taking out the austenitic nickel titanium-based shape memory alloy, performing recrystallization annealing, taking out the memory alloy after reaching the heat preservation time, rapidly putting the memory alloy into water, performing quenching treatment, taking out the material after the material is completely cooled to the room temperature, and air-drying the material; loading the memory alloy cylinder subjected to recrystallization annealing along the axial direction at room temperature for plastic deformation; the method can reduce the deformation resistance of the austenitic nickel-titanium-based shape memory alloy and obviously improve the room-temperature plastic processing performance of the alloy.
Description
Technical Field
The invention belongs to the technical field of metal material processing and manufacturing, and particularly relates to a method for improving room temperature plasticity of an austenitic nickel titanium based shape memory alloy.
Background
Shape Memory Alloy, Shape Memory Alloy (SMA), refers to an Alloy that has an initial Shape, is plastically deformed at a low temperature and fixed into another Shape, and is restored to the initial Shape by heating to a temperature above a certain critical temperature. The function that a shape memory alloy has to remember its original shape is called shape memory Effect. The shape memory alloy is a special novel functional material, is an intelligent material integrating sensing and driving, can be used for manufacturing small and exquisite, highly automatic and reliable components and parts due to unique functions, attracts attention and is widely applied.
Nickel titanium shape memory alloys have been discovered by people since the last 60 s, and are widely used in the fields of medicine, aerospace and military due to their characteristics of good shape memory effect, superelasticity, biocompatibility and the like. The outstanding properties of the nickel-titanium alloy mainly come from the special microstructure of thermoelastic martensite, twin crystal, grain boundary, dislocation and the like. Due to the rapid development of modern science and technology, the preparation of nickel titanium based shape memory alloy with more excellent performance becomes a research hotspot of various scholars. Meanwhile, the modern nano material has excellent physical properties, so that the nano material also becomes the key point of development strategies of various countries. The metal plastic crystal theory originates in the 20 th century, and the plastic structure of single crystal materials and polycrystalline materials can reveal the plastic deformation mechanism of metal materials, and the technology plays an important role in the metal plastic processing theory and actual production along with the development of finite element simulation technology. The finite element analysis means can carry out scientific prediction, parameter optimization and process control on the plastic forming of the metal, and a large amount of manpower, material resources and financial resources are saved. Among all shape memory alloys reported at present, nickel titanium based shape memory alloys have attracted attention because of high strength and good corrosion resistance, and thus have been widely used in the fields of aerospace, ships, ground weapons, biomedical materials, and the like. Due to the poor room temperature plasticity of nitinol-based shape memory alloys, thermoplastic deformation and thermo-mechanical processing are common methods for processing such alloys. However, the surface of the forging is usually oxidized by plastic forming at high temperature, and the dimensional accuracy of the part is not high, so that the part cannot be directly used. Therefore, people are always looking for a method for improving the room temperature plasticity of the nickel titanium based shape memory alloy so as to obtain a product with good comprehensive mechanical property and dimensional accuracy at room temperature. The method for realizing the large plastic deformation of the nickel titanium based shape memory alloy at room temperature mainly comprises high-pressure torsion, cold rolling, cold drawing, equal channel angular extrusion and sheath compression. However, the above method can only form blanks with specific shapes or sizes, and cannot form parts with complex shapes. Research shows that the metal material forms deformation texture or recrystallization texture during plastic deformation or heat treatment, and the texture orientation has great influence on the plasticity of the material. Therefore, the invention provides a method for improving the room temperature plasticity of the austenitic nickel titanium based shape memory alloy by adjusting the texture.
Disclosure of Invention
The invention aims to provide a method for improving the room-temperature plasticity of an austenitic nickel-titanium-based shape memory alloy by adjusting texture, improve the cold plastic deformation performance of the austenitic nickel-titanium-based shape memory alloy and realize larger plastic deformation of the austenitic nickel-titanium-based shape memory alloy at room temperature.
The invention specifically comprises the following steps:
step 1: cutting an original bar of the rolled austenite nickel titanium based shape memory alloy 1 into a cylinder with a certain height and then embedding the cylinder into a low carbon steel annular sheath 2 with the same height as the cylinder; the cylinder of the austenitic nickel titanium-based shape memory alloy 1 is in interference fit with the low-carbon steel sheath 2;
step 2: putting the austenitic nickel titanium base shape memory alloy 1 passing through the low carbon steel sheath 2 between an upper anvil plate and a lower anvil plate of a press, and keeping the temperature at room temperature for less than or equal to 0.05s-1The strain rate of the strain is used for carrying out large plastic deformation, and the compression deformation degree in the height direction of the strain reaches 50-75 percent;
and step 3: taking the compressed austenitic nickel titanium-based shape memory alloy 1 of the low-carbon steel sheath 2 out of the low-carbon steel sheath 2, and then putting the low-carbon steel sheath in a vacuum furnace for recrystallization annealing at 800 ℃, wherein the heat preservation time is calculated according to the minimum size of 2-3 min/mm; after the heat preservation time is reached, taking out the austenite nickel titanium base shape memory alloy 1, and quickly putting the austenite nickel titanium base shape memory alloy into water for quenching treatment; after the material is completely cooled to room temperature, taking out and air-drying;
and 4, step 4: and (3) loading the austenite nickel titanium base shape memory alloy 1 cylinder subjected to recrystallization annealing along the axial direction at room temperature for plastic deformation.
The step 1 specifically comprises:
the inner diameter of the low-carbon steel annular sheath 2 is the same as the diameter of the austenitic nickel titanium base shape memory alloy cylinder 1, and the outer diameter of the low-carbon steel annular sheath is 3-4 times of that of the austenitic nickel titanium base shape memory alloy; the ratio of the height of the low-carbon steel annular sheath 2 to the outer diameter thereof is less than or equal to 2.5.
Compared with the prior art, the invention has the following advantages:
1. the room temperature plasticity of the austenite nickel titanium base shape memory alloy can be obviously improved by the method, the deformation resistance is reduced, and the room temperature plastic processing performance of the alloy is obviously improved.
2. The method is beneficial to improving the plastic deformation of the austenite nickel titanium base shape memory alloy at room temperature, and has important value for improving the super-elastic performance of the austenite nickel titanium base shape memory alloy through cold plastic deformation.
Drawings
FIG. 1 is a schematic diagram of a method for improving room temperature plasticity of austenitic nickel titanium-based shape memory alloy by adjusting texture;
FIG. 2 is an axial <110> texture of an austenitic nickel titanium based shape memory alloy in an as-rolled condition;
FIG. 3 is an axial <111> texture of austenitic NiTi-based shape memory alloy subjected to jacket compressive plastic deformation and static recrystallization;
FIG. 4 is a graph of a distribution of Schmidt factor values for loading an austenitic nickel titanium based shape memory alloy in different orientations;
FIG. 5 is the axial true stress-true strain curve of austenitic Ni-Ti-Fe shape memory alloy before and after sheath compression plastic deformation and recrystallization annealing;
Detailed Description
The following description of the embodiments of the present invention is provided with reference to the accompanying drawings:
as shown in fig. 1, the invention of the present invention is as follows, step 1: a rolled austenite nickel titanium base shape memory alloy original bar is cut into a cylinder with a certain height and then is embedded into a low carbon steel annular sheath with the same height. The inner diameter of the sheath is the same as the diameter of the austenite nickel titanium base shape memory alloy cylinder, and the outer diameter of the sheath is 3-4 times of that of the austenite nickel titanium base shape memory alloy. The ratio of the height of the sheath to the outer diameter thereof should be less than or equal to 2.5. The austenitic nickel titanium-based shape memory alloy cylinder and the low-carbon steel sheath are in interference fit.
Step 2: putting the sheathed austenite nickel titanium base shape memory alloy between an upper anvil plate and a lower anvil plate of a press machine, and performing room temperature treatment on the austenite nickel titanium base shape memory alloyIn 0.05s or less-1The strain rate of (2) is to perform large plastic deformation, namely, the degree of compression deformation in the height direction reaches 50-75%.
And step 3: and taking the austenite nickel titanium base shape memory alloy after the sheath is compressed out of the sheath, and then putting the austenite nickel titanium base shape memory alloy in a vacuum furnace for recrystallization annealing at 800 ℃, wherein the heat preservation time is calculated according to the minimum size of 2-3 min/mm. And after the heat preservation time is reached, taking out the austenite nickel titanium base shape memory alloy, and quickly putting the austenite nickel titanium base shape memory alloy into water for quenching treatment. And taking out the material after the material is completely cooled to room temperature and air-drying the material.
And 4, step 4: the austenite nickel titanium base shape memory alloy cylinder after recrystallization annealing is loaded along the axial direction at room temperature for plastic deformation, and the plastic property is obviously improved and the deformation resistance is obviously reduced.
The principle of the invention is as follows: the austenitic Ni-Ti-based shape memory alloy has a B2 cubic structure, and the slippage system of the alloy is mainly found to be {011}<100>、{110}<111>And {001}<100>Three families, of which {011}<100>The stacking fault energy of the family slip system is about 142mJ/m2，{110}<111>The stacking fault energy of the family slip system is about 660mJ/m2，{001}<100>The stacking fault energy of the family slip system is about 863m J/m2. As can be seen, {011}<100>The group slip system has the lowest stacking fault energy and is most easy to start, so the slip system of the austenitic nickel-titanium-based shape memory alloy is {011}<100>The family is the main. In addition, the austenite nickel titanium base shape memory alloy in the rolling state has<110>Texture, while the austenitic Ni-Ti based shape memory alloy subjected to large cold plastic deformation and static recrystallization has axial direction<111>And (5) texturing. When the austenitic Ni-Ti-based shape memory alloy cylinder in the original rolling state is axially loaded, the austenite Ni-Ti-based shape memory alloy cylinder is equivalent to that in the crystal<110>The load is applied in the direction shown in fig. 2. When the cylinder of the austenitic nickel titanium based shape memory alloy treated by the compression plastic deformation and the static recrystallization of the sheath is axially loaded, the axial loading is equivalent to that of the cylinder of the austenitic nickel titanium based shape memory alloy on the crystal<111>The load is applied in the direction shown in fig. 3. When the alloy is plastically deformed under the two different orientations, each crystal in the materialThe Schmitt factor of the particle-slip system is very different, as shown in FIG. 4. It is well known that the schmitt factor is an important parameter for measuring the plasticity of anisotropic materials. The larger the Schmitt factor, the easier the slip system starts at this time, and the better the plasticity of the material. As can be seen from FIG. 4, the high values of the Schmitt factor are mainly concentrated when the austenitic Ni-Ti based shape memory alloy is subjected to different orientation loading<111>And (4) direction. Thus, in<111>When the alloy is loaded in the direction, the plasticity of the alloy is improved, namely, the axial direction of the austenite nickel titanium base shape memory alloy cylinder in the original rolling state can be processed by sheath compression cold plastic deformation and static recrystallization<110>Texture change to<111>Texture, and thus, the plasticity when it is deformed axially is significantly improved.
Example (b):
the first step is as follows: the austenite nickel titanium iron shape memory alloy Ni in a rolling state47Ti50Fe3Processing the bar into a cylinder with the diameter of 4mm and the height of 6mm, then embedding the cylinder into a Q235 steel ladle sleeve with the inner diameter of 4mm, the outer diameter of 10mm and the height of 6mm, and Ni47Ti50Fe3The alloy and the Q235 steel sheath are in interference fit.
The second step is that: ni to be coated47Ti50Fe3The alloy was placed between upper and lower anvil plates of a press at room temperature for 0.05s-1The strain rate of (2) was subjected to large plastic deformation with a deformation degree of 50%, i.e., the dimension in the height direction became 1/2 as it was.
The third step: ni after jacket compression47Ti50Fe3The alloy is taken out of the sheath and then placed in a vacuum furnace for recrystallization annealing at 800 ℃. Keeping the temperature for 4min, adding Ni47Ti50Fe3Taking out the alloy, and quickly putting the alloy into water for quenching treatment. And taking out the material after the material is completely cooled to room temperature and air-drying the material.
The fourth step: recrystallization annealed Ni47Ti50Fe3The alloy cylinder is subjected to plastic deformation along the axial direction at room temperature, so that the plasticity is obviously improved, and the deformation resistance is also improvedAnd significantly decreased as shown in fig. 5.
Claims (2)
1. A method for improving room temperature plasticity of austenitic nickel titanium based shape memory alloy by adjusting texture specifically comprises the following steps:
step 1: cutting an original bar of the rolled austenite nickel titanium base shape memory alloy (1) into a cylinder with a certain height and then embedding the cylinder into a low-carbon steel annular sheath (2) with the same height as the original bar; the cylinder of the austenitic nickel titanium-based shape memory alloy (1) is in interference fit with the low-carbon steel annular sheath (2);
step 2: placing the austenitic nickel titanium-based shape memory alloy (1) which passes through the low-carbon steel annular sheath (2) between an upper anvil plate and a lower anvil plate of a press machine, and carrying out large plastic deformation on the austenitic nickel titanium-based shape memory alloy at room temperature at a strain rate of less than or equal to 0.05s < -1 >, wherein the degree of compression deformation in the height direction of the austenitic nickel titanium-based shape memory alloy reaches 50% -75%;
and step 3: taking the compressed austenitic nickel titanium-based shape memory alloy (1) of the low-carbon steel annular sheath (2) out of the low-carbon steel annular sheath (2), and then putting the low-carbon steel annular sheath in a vacuum furnace for recrystallization annealing at 800 ℃, wherein the heat preservation time is calculated according to the minimum size of 2-3 min/mm; after the heat preservation time is reached, taking out the austenite nickel titanium base shape memory alloy (1), and quickly putting the austenite nickel titanium base shape memory alloy into water for quenching treatment; after the material is completely cooled to room temperature, taking out and air-drying;
and 4, step 4: and (3) loading the austenite nickel titanium base shape memory alloy (1) cylinder subjected to recrystallization annealing along the axial direction at room temperature for plastic deformation.
2. The method for improving the room temperature plasticity of the austenitic nickel titanium based shape memory alloy by adjusting the texture as claimed in claim 1, wherein the step 1 specifically comprises:
the inner diameter of the low-carbon steel annular sheath (2) is the same as the diameter of a cylinder of the austenitic nickel titanium based shape memory alloy (1), and the outer diameter of the low-carbon steel annular sheath is 3-4 times of that of the austenitic nickel titanium based shape memory alloy; the ratio of the height of the low-carbon steel annular sheath (2) to the outer diameter thereof is less than or equal to 2.5.
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| CN111468553B (en) * | 2020-04-08 | 2021-04-20 | 重庆理工大学 | Nickel-titanium shape memory alloy plate with gradient grain structure |
| CN113559333B (en) * | 2021-06-07 | 2022-11-08 | 中国科学院金属研究所 | Medical nickel-titanium alloy with high anticoagulation function without surface treatment |
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| CN102251200A (en) * | 2011-05-26 | 2011-11-23 | 哈尔滨工程大学 | Method for improving compressive plasticity of Ni-Ti shape memory alloy by sheathing way |
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